What is CVE-2026-77521?

CVE-2026-77521 is MaxKB: Prompt-injectable agent can lead to command execution. The supplied enrichment data classifies it as Remote Code Exec mapped to CWE-78 OS Command Injection; CWE-250 CWE-250; CWE-749 CWE-749.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-77521. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-77521 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-77521. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS, EDR process telemetry, host service logs where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-77521 using CVSS 10, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

criticalRemote Code Exec

CVE-2026-77521

CVE-2026-77521 — MaxKB: Prompt-injectable agent can lead to command execution

MaxKB is an open-source AI assistant for enterprise. Prior to version 2.10.5-lts, assistants with a tool, MCP tool, skill, or sub-application use SandboxShellBackend, which exposes an execute shell tool without excluding it and omits execute from interrupt_on, so human approval is not required. Untrusted chat or ingested content can therefore cause command execution; source deployments with MAXKB_SANDBOX disabled run commands directly as the application user, while the official root container's string-based gosu wrapper allowed shell metacharacters to execute outside the intended sandbox. This issue is fixed in version 2.10.5-lts.

Published Sep 21, 2026Updated Sep 21, 2026Sources: NVD, 1Panel-dev (CNA), GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

ahead of 0% of scored CVEs

Affects

1Panel-dev

MaxKB

CVSS base

critical

Remediation

The vendor's own words where we have them.

Upgrade MaxKB to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
1Panel-dev	MaxKB	< 2.10.5-lts	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Changed

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
10	CVSS 3.1	critical	3.9	6	GitHub (CNA), 1Panel-dev (CNA)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-250 · Execution with Unnecessary Privileges

Gain Privileges or Assume Identity
Execute Unauthorized Code or Commands
Read Application Data
DoS: Crash, Exit, or Restart

Mitigation: Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.

CWE-749 · Exposed Dangerous Method or Function

Gain Privileges or Assume Identity
Read Application Data
Modify Application Data
Execute Unauthorized Code or Commands

Mitigation: If you must expose a method, make sure to perform input validation on all arguments, limit access to authorized parties, and protect against all possible vulnerabilities.

Weakness & attack patterns

CWE-78OS Command Injection
CWE-250
CWE-749

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-15 · Command DelimitersCAPEC-88 · OS Command InjectionCAPEC-43 · Exploiting Multiple Input Interpretation LayersCAPEC-108 · Command Line Execution through SQL InjectionCAPEC-6 · Argument Injection

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable MaxKB.

web/proxy/WAF logsapplication logsnetwork IDS/IPSEDR process telemetryhost service logs

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 10.0 (AV:N)
Sep 21, 2026 · NVD
Initial · CVE published
Sep 21, 2026 · NVD
CVE published by MITRE.
Sep 21, 2026 · SOCRadar CTI

References

3 on the record

github.com/1Panel-dev/MaxKB/commit/594f50f2ea80a502d1c955371ba0438b277c30ea
Exploit, Third Party Advisory, Mitre
github.com/1Panel-dev/MaxKB/releases/tag/v2.10.5-lts
Exploit, Third Party Advisory, Mitre
github.com/1Panel-dev/MaxKB/security/advisories/GHSA-f36j-f34j-h3rx
Exploit, Third Party Advisory, Mitre

Elsewhere on this site

1Panel-devevery CVE for this vendor
Remote Code Execsame class
CWE-78other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-77521 is MaxKB: Prompt-injectable agent can lead to command execution, a critical vulnerability affecting MaxKB from 1Panel-dev. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-77521. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-77521. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 10 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.